1. Technical Field
The disclosure relates to a method for fabricating a heat pipe and an instrument of the method, and in particular relates to a method for fabricating a heat pipe with high heat transfer performance and an instrument of the method.
2. Related Art
Heat pipes have excellent heat transfer performance due to their low thermal resistance, and are therefore an effective means for the transfer or dissipation of heat from heat sources. Currently, heat pipes are widely used for removing heat from heat-generating components such as central processing units (CPUs) of computers.
Generally, according to the positions from which heat is input or output, the heat pipe has three sections: an evaporating section, a condensing section and an adiabatic section between the evaporating section and the condensing section.
The adiabatic section is typically used for transport of the generated vapor from the evaporating section to the condensing section. When the evaporating section of a heat pipe is thermally attached to a heat-generating electronic component, the working fluid receives heat from the electronic component and evaporates. The generated vapor then moves towards the condensing section of the heat pipe under the vapor pressure gradient between the two sections. In the condensing section, the vapor is condensed to a liquid state by releasing its latent heat to, for example, a heat sink attached to the condensing section. Thus, the heat is removed away from the electronic component.
Then the condensed liquid (the working fluid has high specific heat capacity, density, and low viscosity) flows to the evaporating section along the capillary configuration of the heat pipe. This evaporating/condensing cycle repeats and since the heat pipe transfers heat so efficiently, the evaporating section is kept at or near the same temperature as the condensing section of the heat pipe. Correspondingly, the heat-transfer capability of the heat dissipation device including the heat pipe is improved greatly.
The heat transfer performance of the heat pipe depends on three major parameters: pore size between powders for forming the heat pipe, porosity of the heat pipe, and permeability of the heat pipe. Regarding a sintered heat pipe, the above parameters can be adjusted by following process conditions: geometry of the sintering powder, average pore size of the sintering powder, and the sintering period.
The evaporating section, condensing section and adiabatic section of a heat pipe respectively have specific requirements of the three major parameters. Ideally, the evaporating section of the heat pipe should have a lower particular size of sintering powder, and the condensing section and adiabatic section of the heat pipe should have a higher particular size of the sintering powder, since the evaporating section demands high capillary force for recovering the working fluid and broad evaporation area for performing a heat exchange, and the condensing section and adiabatic section demand low fluid impedance for facilitating the liquid transport.
In order to obtain a heat pipe having portions with different particular sizes of sintering powders, a conventional method employs at least two powders with different particular sizes for fabricating a heat pipe. The above method, however, leads to a low product yield and increases the process complexity, and is not suitable for mass production.